“Rivers like that were prehistoric highways,” said Albert Goodyear of the South Carolina Institute of Archaeology and Anthropology.

Similar tribal gathering sites have been found on the nearby Broad and Congaree rivers, but Green said none yielded material of this quantity and age.

The site was discovered in 2006 as part of a federally required search of parcels with possible historic significance. That search was among the things required of South Carolina Electric & Gas Co. as part of a review of its lake operations.

It was the first major look for such sites at the lake and river downstream since requirements became mandatory after SCE&G’s previous review 30 years ago.

“We didn’t expect to find something this significant,” said Bill Argentieri, who is overseeing the review for SCE&G.

About 150 tracts around the lake and river were identified as possibly historic. But only the bluff was judged by experts as worth exploring.

And what Green’s team found at the bluff was layers of material left over centuries.

Green was wowed when the dig turned up artifacts estimated at up to 2,000 years old just 3 feet deep.

“We knew there likely was much older stuff much more deeply buried,” he said.

Items found up to 12 feet underground indicate the 10-acre Saluda site was used by a series of Native American tribes that migrated along the Eastern coast, he said. Some material is as recent as 500 years old.

“It’s a very impressive study,” in terms of the breadth of material recovered, Goodyear said. Only one other site in South Carolina has turned up items that old — a Savannah River Valley site near Allendale.

Some rare items, particularly spear points, he said, are “what you hope to find.”

Secrecy surrounded the project to prevent vandalism and keep out the curious. And while the excavation work is finished, SCE&G officials won’t give the exact location, though they noted it is nicknamed Tree House Site, after a nearby landmark.

Half of the excavation site is privately owned — and potentially could be sold for development someday. SCE&G owns the other half, and it plans to ban building there, Green said.

For now, studies of the artifacts are starting under the supervision of S&ME, a St. Andrews firm at which Green works that specializes in such evaluation.

Eventually, some items will be offered to area museums for public display. Others will go to the S.C. Institute of Archaeology and Anthropology.

The Palmetto Trust for Historic Preservation recently gave SCE&G an award for subsidizing exploration of the site. Argentieri declined to reveal the cost.

The Midlands-based utility oversees operations of the 47,500-acre lake built for hydropower and now a popular recreation spot.